Polyprotic acid successive acidity constants table

Protons are donated successively by polyprotic acids, with the acidity constant decreasing significantly, usually by a factor of about 10 , with each proton lost (Table 10.9) ... 

The definition of pH is pH = —log[H+] (which will be modified to include activity later). Ka is the equilibrium constant for the dissociation of an acid HA + H20 H30+ + A-. Kb is the base hydrolysis constant for the reaction B + H20 BH+ + OH. When either Ka or Kb is large, the acid or base is said to be strong otherwise, the acid or base is weak. Common strong acids and bases are listed in Table 6-2, which you should memorize. The most common weak acids are carboxylic acids (RC02H), and the most common weak bases are amines (R3N ). Carboxylate anions (RC02) are weak bases, and ammonium ions (R3NH+) are weak acids. Metal cations also are weak acids. For a conjugate acid-base pair in water, Ka- Kb = Kw. For polyprotic acids, we denote the successive acid dissociation constants as Kal, K, K, , or just Aj, K2, A"3, . For polybasic species, we denote successive hydrolysis constants Kbi, Kb2, A"h3, . For a diprotic system, the relations between successive acid and base equilibrium constants are Afa Kb2 — Kw and K.a Kbl = A w. For a triprotic system the relations are A al KM = ATW, K.d2 Kb2 = ATW, and Ka2 Kb, = Kw. 

The acid-dissodation constants for a few common polyprotic acids are listed in Table 16.3 . A more complete list is given in Appendix D. The stmctures for ascorbic and dtric acids are shown in the margin. Notice that the values for successive losses of protons from these acids usually differ by a factor of at least 10. Notice also that the value of K i for sulfuric add is listed simply as "large." Sulfuric add is a strong add with respect to the removal of the first proton. Thus, the reaction for the first ionization step lies completely to the right ... 

Table 4.5 Successive acidity constants of polyprotic acids at 298.15 K...

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